The United States Golf Association (“USGA”) provides five (5) regulations to keep golf balls consistent. Specifically, the golf ball must weigh no more than 1.62 ounces and measure no less than 1.68 inches in diameter. The initial velocity of the ball as tested on a USGA machine at a set club head speed must not exceed 255 ft/sec. The overall distance of the ball as tested with a USGA specified driver at 160 ft/sec and a 10-degree launch angle must not exceed 296.8 yards. Furthermore, the ball must pass a USGA-administered symmetry test. Within the confines of these regulations, other performance characteristics of the ball, including distance, durability, feel, spin, sound, and the like may be modified through alterations in material compositions, constructions, diameters and/or thickness, and surface configurations of various portions of the ball, such as the core, the cover, and intermediate layer(s) therebetween. Other physical, mechanical, chemical, and/or optical properties of the portions, including color stability, compression, density, flexural modulus, gas or vapor permeability, hardness, stiffness, tear resistance, weight, and the like may also be affected by these alterations.
Conventional cover or intermediate layer materials for golf balls include ionomer resins and polyurethanes. Chemically, ionomer resins are a copolymer of an olefin and an ethylenically unsaturated α,β-carboxylic acid having 10 to 100 percent of the carboxylic acid groups neutralized by a metal ion. Polyurethanes are typically formed from a prepolymer of polyol with isocyanate and a curing agent. Ionomer covers are virtually cut-proof, but they provide inferior spin and feel to the golf balls. Conventional polyurethane covers generally afford excellent feel and good durability, but not resilience or light stability comparable to ionomer covers.
Polyurea has also been proposed as cover materials for golf balls. For instance, U.S. Pat. No. 5,484,870 discloses a polyurea composition comprising the reaction product of an organic diisocyanate and an organic amine. Like polyurethanes, polyurea is not completely comparable to ionomer covers with respect to resilience. Therefore, there remains a continuing need for golf ball materials and compositions with superior resistance to cut, scratch, abrasion, discoloration, moisture, and other wearing and weathering elements, that provide improved performance characteristics such as resilience and feel.